Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $47.91   12.642%   $53.9668   $53.97   $53.95   $54.00  
  Purchase #2 $214.86   6.552%   $228.9376   $228.94   $228.95   $228.90  
  Purchase #3 $165.81   9.634%   $181.7841   $181.78   $181.80   $181.80  
  Purchase #4 $112.61   5.664%   $118.9882   $118.99   $119.00   $119.00  
  Purchase #5 $106.93   7.844%   $115.3176   $115.32   $115.30   $115.30  
  Purchase #6 $143.92   11.834%   $160.9515   $160.95   $160.95   $161.00  
  Purchase #7 $241.44   8.822%   $262.7398   $262.74   $262.75   $262.70  
  7 purchase totals = $1,033.48       $1,122.6856   $1,122.69   $1,122.70   $1,122.70